Fish oil and omega-3 supplements are among the most commonly used health products in the world. Many older adults take these capsules every day in the hope of protecting their memory, keeping their brains healthy, and lowering the risk of dementia.
For years, omega-3 fats have been linked to possible health benefits. They are found naturally in fish and are believed to support heart health, reduce inflammation, and help brain function. Some studies in animals and population research have suggested that people who consume more omega-3 may have better cognitive health as they age.
Because of this, many supplement companies market omega-3 pills as “brain-protecting” products.
However, scientists still disagree about whether these supplements truly help people in real life.
Now, a new study published in The Journal of Prevention of Alzheimer’s Disease is challenging the popular belief that omega-3 supplements are always good for the aging brain.
Researchers from China analyzed long-term cognitive and brain imaging data and found that older adults taking omega-3 supplements appeared to decline mentally faster than those who did not take them.
The study used information from the Alzheimer’s Disease Neuroimaging Initiative, a major long-running research project that tracks brain aging and dementia.
Researchers examined data from 273 omega-3 supplement users and compared them with 546 non-users over a five-year period.
The groups were matched for important factors including age, sex, genetics, and diagnosis to help ensure fair comparisons.
Participants completed several common cognitive tests during the study. These tests measured memory, thinking ability, attention, and overall mental function.
The researchers found that people taking omega-3 supplements performed worse over time across all three major cognitive assessments used in the research.
This pattern remained even after accounting for genetic risk factors.
In particular, the scientists looked closely at the APOE ε4 gene, which is strongly associated with increased Alzheimer’s disease risk.
Both groups contained similar numbers of people carrying this gene, suggesting that genetics alone could not explain the faster decline seen among omega-3 users.
To investigate further, researchers examined detailed brain scans.
The findings were unexpected.
The researchers did not find stronger buildup of amyloid plaques or tau proteins among omega-3 users. These are usually considered the classic biological signs of Alzheimer’s disease.
Instead, the biggest difference involved brain glucose metabolism.
Brain scans showed that omega-3 users experienced a larger decline in the brain’s ability to use glucose for energy.
The brain depends heavily on glucose to power communication between brain cells. When glucose metabolism drops, brain cells may struggle to communicate efficiently even if brain structures themselves still appear relatively normal.
Scientists believe this reduced brain energy activity may reflect problems with synapses, which are the tiny communication connections between neurons.
The researchers suggested that omega-3 supplementation may possibly affect brain function through changes in synaptic activity rather than through traditional Alzheimer’s disease pathways.
However, the authors emphasized that their results are not definitive.
The study was observational, meaning it only observed associations between supplement use and cognitive decline. It cannot prove that omega-3 supplements directly caused the changes.
There may be other explanations.
For example, people already concerned about memory problems may have been more likely to start taking omega-3 supplements in the first place. Other health differences not fully measured in the study may also have influenced the results.
Still, the findings are important because omega-3 supplements are so widely used and generally viewed as safe.
Many people assume that because omega-3 fats are natural and found in fish, supplements must automatically be beneficial.
But scientists say nutrition research is often more complicated than that.
Some previous studies have shown possible benefits of omega-3, especially from eating fish as part of a healthy diet. However, controlled human trials using supplement pills have often failed to show clear cognitive improvements.
Researchers believe the timing, dosage, quality of supplements, and overall health of participants may all affect outcomes.
The study also raises questions about whether getting nutrients from food may work differently than taking concentrated capsules.
Experts continue to recommend healthy lifestyle habits as the strongest evidence-based approach for protecting brain health. Regular exercise, healthy eating, blood pressure control, good sleep, social activity, and avoiding smoking remain some of the most reliable strategies for reducing dementia risk.
The researchers say more clinical trials are needed to understand whether omega-3 supplements may help some groups of people while potentially harming others.
Overall, the study highlights the need for caution when interpreting supplement claims and reminds people that products marketed for brain health may not always deliver the benefits people expect.
If you care about nutrition, please read studies about a breakfast linked to better blood vessel health, and drinking too much coffee could harm people with high blood pressure.
For more information about health, please see recent studies about unhealthy habits that may increase high blood pressure risk, and results showing plant-based protein foods may help reverse diabetes.
Source: Alzheimer’s Disease Neuroimaging Initiative.
